Genome-wide association studies have identified 6 genes and genetic loci associated with RLS, namely, MEIS1, BTBD9, PTPRD, MAP2K5/SKOR1, TOX3, and the intergenic rs6747972 on chromosome 2; none of these markers have been associated with PD.[25] However, it is possible that an unknown gene may be involved in the relationship between RLS and PD. The gene discussed is BTBD9; the disease is Parkinson disease.